Petroleum-derived solvents and fuels are of environmental concern and are under legislative to be replaced by biodegradable substitutes that afford reduced environmental impact. Unpredictable petroleum prices and the increasing desire for energy independence and security have led to burgeoning research activities directed toward developing a variety of alternative fuels. Among these new fuels, biodiesel is a biodegradable, nontoxic diesel that can be produced by transesterification of various oil feedstocks, including vegetable oils, animal fats, algal oils, and restaurant waste oils. Examples of biodiesel can include fatty acid C1-5 alkyl esters, such as soy diesel (methyl soyate), rapeseed methyl ester, and various vegetable and animal fat methyl esters. Biodiesel has been accepted worldwide as a viable alternative to traditional petroleum-derived solvents and fuels. Free fatty acids in the feedstocks for bio-diesel production can negatively affect the process and resulting product. For example, free fatty acids can react with catalysts used for transesterification, forming soaps and consuming catalyst. The efficiency and efficacy of biodiesel production can be greatly increased by reducing the concentration of free fatty acid in the feedstock.
Catalysts are essential materials in a wide variety of useful and important chemical reactions. Generally, catalysts are unselectively exposed to materials in a chemical reaction. Therefore, a molecule at lower concentration with a particular reactivity with the catalyst has a lower chance of undergoing the chemical change caused by the catalyst than a different molecule at a higher concentration having the same reactivity with the catalyst.